In the production of sodium chlorate, an aqueous solution of sodium chloride is electrolyzed in a diaphragmless cell and the liquid products of electrolysis are allowed to react to form sodium chlorate. The overall reaction may be represented as follows: EQU NaCl + 3H.sub.2 O .fwdarw. NaClO.sub.3 + 3H.sub.2
generally, small amounts of oxygen are formed at the anode surface due to side reactions and the evolved oxygen appears in the hydrogen off-gas stream at concentrations of the order of 1 to 2% of the total off-gas volume. The formation of oxygen in this way represents a loss of potential chlorate product, and hence the larger the amount of oxygen produced, the more inefficient is the cell.
Platinum alloy-coated titanium electrodes have been used as anodes in chlorate cells and, particularly, in the case of platinum-iridium alloy coated electrodes, in some instances, upon extended use greater than normal oxygen production has been observed, typically about 31/2 to 4% oxygen in the off-gas stream, representing a deterioration of the efficiency of the electrode.